In the use of computer controlled printers it has become desirable that the output from the printer be collected in sorter trays to separate multiple copies of a job. In addition, particularly in the case of networked printers, it has become desirable to be able to separately collect different jobs in the sorter trays in the manner of a mailbox, so that the jobs or work output for different users may be isolated from one another.
It also has become desirable that the separate jobs which may be of a sensitive nature may be secured against unauthorized access, so that locking mailbox type sorter constructions have evolved.
Printers which operate at relatively high speeds of, say, 40 pages per minute are faster and generally with small gaps between pages or between the last page of one job and the first page of another job, may require truly, almost instantaneous, random access to different trays. Sheet sorting or collating machines of the type using instantaneously and selectively operable means for deflecting sheets from the sorter sheet transport to the selected trays are preferably employed for such high speed printers.
Examples of such sorters are shown and described, for example, in my prior U.S. Pat. Nos. 3,937,459 and 4,691,914.
In the case of U.S. Pat. No. 3,937,459, a series of vertically spaced gates are arranged to be actuated by solenoids to deflect sheets from a vacuum plenum type transport, into the trays which are arranged in a vertical stack. The only speed limitation on such a sorter and other so-called fixed bin, gate type sorters is the time required for the gates to move from a normal sheet guiding position to a sheet deflecting position, so that such sorters are very well suited to use as true random access mailboxes, as referred to above. In addition, the gates are of nesting construction to reduce the overall height of the apparatus while providing a guide for sheets passing the gates.
In the case of U.S. Pat. No. 4,691,914, the sheet path is defined by opposing sets of rollers carried by a modular stack of sheet transport units, and a solenoid operated nip roller is moved to a position cooperative with one of the fixed rollers to divert or deflect a sheet into a selected tray. Such a sorter construction is more simple in construction than the sorter of U.S. Pat. No. 3,937,459 and lends itself to selecting the number of trays and the height of the assembly due to its modular construction. Again, such a sorter is applicable to relative high speed printers because it can be randomly operated substantially instantaneously.
Another prior sorter useful with high speed printers is shown in U.S. Pat. No. 4,881,730. In this construction the sorter employs a combination of sheet transport rollers and pivoted gates to deflect sheets from the transport rolls to the trays.
As shown in U.S. Pat. No. 4,111,410 vertically spaced sets of feed rollers transport the sheets to the tray entry space and gates are opened to deflect sheets from the rollers, while the sheet inlet ends of the trays are held spaced apart to increase the inlet space.
These types of sorters referred to above are inherently expensive, due to the numbers of components and the size of the sorter assemblies required to sort or collate the output of sheets from a source machine, either sequentially or randomly. However, such sorters are fast because they eliminate the time delays inherent in sorter devices of the types employing travelling infeeds, as exemplified in my U.S. Pat. No. 4,843,434 or travelling deflectors, as exemplified in Snellman U.S. Pat. No. 3,372,922, dated Mar. 12, 1968, or travelling sheet gripping infeeds, as exemplified in U.S. Pat. No. 4,881,730, or the lockbox sorter disclosed in the application of Coombs and Billings, U.S. Ser. No. 849,233 (owned in common herewith) in which the gates are selectively operable by an indexed actuator which also can release a lockbox. These latter types of sorter devices are not as well suited for high speed printer mailboxes because of the time delay required to provide for transfer of a sheet to different bins.